1. Field of the Invention
This invention relates to an endoscope for medical or industrial purposes, for example, for internal examination or diagnosis of patients' bodies, engines, nuclear reactors or other equipment.
2. Description of the Prior Art
An endoscope generally comprises a control unit, an insert portion connected to the control unit to be inserted into the inner cavity of human body or machine to be inspected, and a universal cord connected to a light source (or a combination of a light source and a processor with an electronic endoscope). The insert portion generally has, from the side of the control unit, a flexible section comprising a greater part of the insert portion which can be curved in any direction along the course of insertion, a bending section connected to the remotest end of the flexible section, and a distal end section connected to the end of the bending section. At the foremost end or the side of the distal end section there is provided an observation window, a light emitting window, an instrument gateway, etc. The bending portion is so designed as to direct the distal end portion toward the desired direction. To permit this operation, the bending section has a series of rings forwarding pivotal joints so as to facilitate being bent vertically or in both a vertical and horizontal direction by pushing and pulling control wires provided between the control unit and the distal end section of the insert portion or the tip end of the bending ring.
In addition to the control wires, a light guide in the form of an optical fiber bundle for emitting light is provided in the insert portion. Also, other lengthwise members are placed throughout the insert portion, such as an image guide fiber bundle for transmitting the image of the object to be observed in an optical endoscope and a cable connected to a solid image pickup means in an electronic endoscope. Further, provided therethrough are, for example, a channel to pass through forceps or other instruments and a fluid duct to feed a detergent and air to wash the observation window. All these lengthwise members mounted in the insert portion are flexible so that they can be deformed by being bent or being curved by the flexible and bending sections thereof.
When the insert portion is bent or curved, length differences arise regarding the members along with the side of inner periphery and the outer side periphery of the curved portion. The bending section, in particular, is so designed a to be bent over 180.degree. in order to allow broader observation of the target. Thus, a considerable length difference of the lengthwise members will exist when these members are positioned either on the inner side or outer sides of the curved portion. Because the bending section can normally be bent in both vertical and horizonal directions, all members in the insert section are moved in arbitrary directions. To prevent damage by the excessive tension or compression on the bending section when being bent, each member is made extra long so as to allow for their axial movements to a predetermined degree.
The insert section must be as thin as possible so that it can be smoothly passed through narrow parts of the insertion passage without causing significant pain to the patient being inspected. As a consequence, there is a great deal of concern regarding the space required by the members in the insert section.
When an endoscope thus constructed is operated so as to bend the bending section, the members in the insert section move arbitrarily, thereby pressing, pushing or twisting each other, resulting in breaking the extra-fine optical fibers of the light guide and the image guide or cables of an electronic endoscope and causing kinks in the instrument channel or fluid ducts. During repeated operation of the endoscope, in particular, such lengthwise members in the insert section are gradually gathered and jammed in the bending section by being bent at large angles, and therefore the density of these members becomes extraordinary high at this particular portion. If the insert section is bent under this highly crowded condition, the aforesaid risks of breaking and kinking will be further increased.
There is known a method of keeping the members in the insert section respectively at the fixed positions in order to prevent their twinning, contacting and pressing each other by filling the bending section with foamed plastic materials. The foamed plastic thus packed in the bending section facilitates not only preventing movement of the members positioned therein but also exhibits a shock absorbing function, thereby reducing the possibility of damage. But this prior art is not completely problem-free.
The foamed plastic filled in the bending section causes increased resistance against the bending thereof, thus increasing the bending torque and impeding smooth operation thereof. Further, there is means in the prior art for control the movement of the members located in the flexible section so that there is thus no way to prevent their meandering or twinning therein.
The control wires for turn or bending the bending section are normally provided at four points in this section, i.e., at the top, bottom, right and left, at angular intervals of 90.degree. to one another. However, these control wires are wound on a pair of pulleys coaxial with bending knobs mounted on the side of the control unit so that the wires are not fixed in the flexible section. Upon operation of the bending section, therefore, the instrument channel, fibers of the light guide and image guide may easily be pinched between the control wires and be damaged. Such a problem can not be avoided by the prior art. Especially, the greater part of the insert portion is constituted by the flexible section having no mean to fix the content members and these members secured at the distal end section, so that when repeatedly operating the bending action, these lengthwise members are pulled toward the bending section so as to be gathered and jammed therein, thereby increasing the risk of pinching and damaging them by the control wires in the flexible section.
Foamed plastic can be filled not only in the bending section but also in the entire insert portion including the flexible section. By so doing, greater protection is available to the content members, but this causes detrimental disadvantages such as the bending section becoming heavier.